Ethylene Oxide in Spices and Botanical Supplements: The Sterilization Contaminant US Brands Still Aren't Testing For

The first warning signs came from sesame seeds. In September 2020, European food safety authorities began flagging Indian sesame imports at an accelerating rate — hundreds of lots with ethylene oxide residues far exceeding EU limits. What started as a single commodity alert cascaded into one of the largest food recall events in European history, pulling tahini, hummus, artisan bread, infant formula, and thousands of finished products from supermarket shelves across the continent. By 2022, EtO-related notifications in the EU’s Rapid Alert System for Food and Feed (RASFF) exceeded 1,000 in a single calendar year, making it the single leading food safety alert category across all of Europe.

Most US supplement and food brands watched that story unfold from a distance. They probably shouldn’t have.

What Ethylene Oxide Is — and Why It’s Still Used in Spices

Ethylene oxide (EtO) is a highly reactive epoxide gas with a deceptively simple use case: it kills microorganisms. Mold, bacteria, and other pathogens can’t survive exposure to it. For spice processors and herbal ingredient suppliers dealing with high microbial loads — a persistent challenge with botanicals grown in tropical climates and dried in open air — EtO fumigation is cheap, effective, and fast. It penetrates bulk materials that steam sterilization and irradiation sometimes can’t reach uniformly, and it leaves no visible trace in the finished ingredient.

The problem is what it leaves behind that you can’t see. The International Agency for Research on Cancer (IARC) classifies ethylene oxide as a Group 1 carcinogen — the same tier as asbestos and tobacco smoke. It’s mutagenic, it alkylates DNA, and epidemiological data from occupationally exposed workers link it to elevated rates of lymphoma and leukemia. The EPA reached similar conclusions in its risk assessments, classifying EtO as “likely to be carcinogenic to humans by all routes of exposure.”

There’s also a secondary contamination concern. When EtO reacts with chloride ions naturally present in food matrices — which is common — it generates 2-chloroethanol (2-CE), a reaction product that’s also toxic and considerably more chemically stable than EtO itself. By the time a product reaches a testing lab, EtO may have partially dissipated, but 2-CE remains as a chemical marker of prior fumigation. A result that shows low EtO paired with elevated 2-CE isn’t a clean result — it’s a flag.

The Regulatory Gap Leaving US Brands Exposed

Here’s where things get complicated for brands operating in both markets, or simply buying ingredients from a global supply chain.

The European Union set a maximum residue level (MRL) for ethylene oxide in herbs and spices at 0.02 mg/kg under Regulation (EC) No 396/2005. That’s effectively near-zero tolerance. Any lot exceeding 0.02 ppm triggers a mandatory recall notification through RASFF.

US regulations operate under a different framework. The EPA establishes pesticide chemical tolerances under 40 CFR Part 180, and EtO tolerances for certain spice and food ingredient categories have historically been set at substantially higher levels — in the range of 7 ppm for some commodities. That’s roughly 350 times more permissive than the EU limit.

The practical consequence: a botanical ingredient lot that clears every US regulatory threshold can still be seized at EU borders or trigger a recall of finished products distributed in Europe. We’ve seen this dynamic play out with international brands that assumed domestic compliance equaled global compliance. It doesn’t — and as the EU’s recall history shows, the enforcement machinery is real.

And even for brands selling exclusively in the US market, the calculus is shifting. Consumer awareness of EtO as a carcinogen has grown sharply since the European recall wave. Some major US retailers and e-commerce platforms have begun tightening restricted substance requirements in ways that go beyond current FDA tolerance levels. The regulatory floor is a starting point, not a ceiling — and treating it as a ceiling is increasingly a business risk, not just a regulatory one.

Why Botanical Supplement Brands Are the Highest-Risk Category

Dietary supplement brands formulating with herbal extracts face a specific vulnerability that food manufacturers don’t always share: the sheer volume and sourcing complexity of botanical raw materials.

A single immune-support formula might source ashwagandha from India, black pepper extract (piperine) from Vietnam, elderberry from Poland, and coriander seed from Morocco. Each botanical has its own microbial profile, its own sterilization history, and its own potential for EtO treatment at some point in the supply chain. The contract manufacturer may hold a total aerobic plate count spec under USP <2021> — but have no incoming testing requirement specifically for EtO or 2-CE residues.

That gap is real and relatively common. In our experience reviewing testing programs for supplement brands, targeted testing for residual EtO or 2-chloroethanol at the raw material stage is the exception, not the standard practice. Yet the ingredients most frequently treated with EtO are precisely the ones supplement brands use at highest volume: dried herbs, powdered botanicals, seed-based extracts, and spice-derived actives.

The risk is compounded by FDA’s current GMP framework for dietary supplements. 21 CFR Part 111 requires identity, purity, strength, and composition testing for incoming raw materials — but EtO residues are not called out as an explicit requirement in the regulation’s text. A brand can be fully GMP-compliant on paper and still be distributing products with EtO contamination it has never tested for. That’s not a loophole; it’s a genuine gap in how the supplement GMP rules were written, and brands shouldn’t wait for FDA to close it before acting.

How Laboratories Actually Test for EtO Residues

Testing for ethylene oxide in botanical ingredients requires headspace gas chromatography coupled with mass spectrometry (HS-GC-MS). The headspace approach is well-suited to EtO and 2-CE because it captures volatile and semi-volatile compounds from the sample matrix without requiring solvent extraction steps that could cause EtO to dissipate before analysis.

In a properly validated method, the lab heats a sealed sample vial to a controlled temperature, concentrating volatiles in the headspace above the matrix, then injects that gas directly into the GC-MS system. Modern instrumentation can reliably detect EtO at concentrations below 0.01 mg/kg — well below the EU’s 0.02 mg/kg MRL — which means there’s no analytical reason to accept uncertainty about whether a borderline lot has been cleared.

A few practical points that matter when submitting samples:

Because EtO off-gasses relatively quickly under ambient conditions, the timing of sample collection and handling matters. Samples should be sealed promptly after collection and shipped chilled to minimize EtO loss before analysis. 2-chloroethanol, by contrast, is far more stable and will persist in the sample matrix much longer. Asking your lab to test for both EtO and 2-CE gives you a more complete picture — especially if there’s any gap between ingredient receipt and sample submission.

Method validation against a matrix-matched blank also matters here. EtO analysis in complex botanical matrices (dense powders, high-fat seed extracts) can be susceptible to matrix suppression effects. Ask your lab whether its method has been validated in matrices representative of what you’re submitting, not just in a simple reference standard.

What to Do Now If You Source Botanical Ingredients

The most immediate step is supplier qualification. If you source herbs, spices, or botanical extracts from origins with documented EtO use — India, Egypt, Ethiopia, and Vietnam appear frequently in RASFF notifications — request written disclosure of sterilization method. A supplier unwilling to confirm whether EtO fumigation is part of their process is, functionally, answering your question.

Second, build EtO and 2-chloroethanol into your incoming raw material testing panel for high-risk categories. This doesn’t need to apply to every ingredient in your portfolio. Start with powdered botanicals from South Asian and African origins, seed-based extracts with historically high microbial loads, and any ingredient where your supplier has been reluctant to share sterilization documentation. Testing 10 to 15 representative lots over a 6-month period builds a meaningful baseline with manageable cost.

Third, understand what EtO-free sterilization alternatives your suppliers can offer. Steam sterilization and gamma irradiation are both established options. Neither leaves the same residue profile as EtO. Both have tradeoffs: high-heat steam can degrade heat-sensitive actives, and gamma irradiation at bactericidal doses requires label disclosure in some markets. These are sourcing conversations, not lab conversations — but having analytical data in hand makes them far more productive.

Finally, if you’re selling into the EU, Canada, or any market where EtO limits are tighter than current US tolerances, treat the strictest applicable MRL as your internal specification. Designing your raw material qualification program around the most restrictive standard in your distribution footprint is simply sound risk management, and it gives you supply chain flexibility as regulations continue to evolve.

Turnaround for HS-GC-MS EtO testing is typically 5 to 10 business days at an ISO 17025 accredited lab — fast enough that, planned correctly, it doesn’t materially disrupt standard sourcing lead times.

The European recall wave wasn’t a European problem. It was a global supply chain problem that Europe detected first, because Europe had the regulatory sensitivity to catch it. US brands that treat it as someone else’s cautionary tale are placing a bet on regulatory inertia that’s getting harder to justify.

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Written by Nour Abochama, Vice President of Operations, Qalitex Laboratories. Learn more about our team

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